The heavy-ion radiative capture reaction C-12(O-16,gamma)Si-28 has been studied at three energies E-c.m. = 8.5, 8.8, and 9 MeV which are close to the Coulomb barrier. The weak radiative capture process has been identified by measuring the Si-28 recoils in the highly selective 0 degrees spectrometer DRAGON at TRIUMF (Vancouver). The coincident gamma rays have been recorded in the associated BGO array. This has allowed a complete measurement of the gamma spectrum and the relative strength of all decay pathways. An important part of the decay through quasibound states close to the particle threshold and the feeding of bound states with particular deformation have been identified for the first time. Comparisons with Monte Carlo simulations allowed the extraction of the full experimental radiative capture cross section. Our results suggest an important contribution of spins J(pi) = 5(-) and 6(+) in the entrance channel. The surprisingly large cross sections from 12 mu b at E-c.m. = 8.5 MeV to 25 mu b at E-c.m. = 9.0 MeV for the heavy-ion radiative capture process are discussed in terms of the interplay between statistical and structural aspects of the process.

The heavy-ion radiative capture reaction ${}^{12}$C(${}^{16}$O,$\ensuremath{\gamma}$)${}^{28}$Si has been studied at three energies ${E}_{\mathrm{c}.\mathrm{m}.}=8.5$, 8.8, and 9 MeV which are close to the Coulomb barrier. The weak radiative capture process has been identified by measuring the ${}^{28}$Si recoils in the highly selective 0${}^{\ensuremath{\circ}}$ spectrometer DRAGON at TRIUMF (Vancouver). The coincident $\ensuremath{\gamma}$ rays have been recorded in the associated BGO array. This has allowed a complete measurement of the $\ensuremath{\gamma}$ spectrum and the relative strength of all decay pathways. An important part of the decay through quasibound states close to the particle threshold and the feeding of bound states with particular deformation have been identified for the first time. Comparisons with Monte Carlo simulations allowed the extraction of the full experimental radiative capture cross section. Our results suggest an important contribution of spins ${J}^{\ensuremath{\pi}}={5}^{\ensuremath{-}}$ and 6${}^{+}$ in the entrance channel. The surprisingly large cross sections from 12 $\ensuremath{\mu}$b at ${E}_{\mathrm{c}.\mathrm{m}.}=8.5$ MeV to 25 $\ensuremath{\mu}$b at ${E}_{\mathrm{c}.\mathrm{m}.}=9.0$ MeV for the heavy-ion radiative capture process are discussed in terms of the interplay between statistical and structural aspects of the process.

Resonances in the 12C(16O,γ)28Si radiative capture process at energies around the Coulomb barrier have been probed using the very selective 0° Dragon spectrometer at Triumf and its associated BGO γ‐array. For the first time the full level scheme involved in this process has been measured and shows previously unobserved γ‐decay to doorway states around 11 MeV in 28Si.

In a recent experiment performed at Triumf using the Dragon 0 degrees spectrometer and its associated BGO array we have measured for the first time the full gamma decay of the radiative capture channel close to the Coulomb barrier. This measurement has been performed at 3 energies E-cm=8.5, 8.8 and 9 MeV. We have extracted a radiative capture cross section more than five times larger than what had been previously observed. A selective contribution of the entrance spins 5(-) and 6(+) has also been evidenced whereas 1(-) to 3(-) spins are predicted to be predominant by coupled-channel calculations. At E-cm=9 MeV, stronger structural behaviour appears which is characterised by a larger total cross section and also by the particularly strong feeding of the Si-28 prolate 4(+) state at 9.16 MeV. This level is explained by several models in terms of C-12-O-16 cluster sub-structure. Our data is compared to such cluster-model predictions and the agreement is quite good.

Resonances in the 12C(16O,γ)28Si radiative capture process at energies around the Coulomb barrier have been probed using the very selective 0° Dragon spectrometer at Triumf and its associated BGO γ‐array. For the first time the full level scheme involved in this process has been measured and shows previously unobserved γ‐decay to doorway states around 11 MeV in 28Si.

Resonances in the C-12(O-16,gamma)Si-28 radiative capture process at energies around the Coulomb barrier have been probed using the very selective 0 degrees Dragon spectrometer at Triumf and its associated BGO gamma-array. For the first time the full level scheme involved in this process has been measured and shows previously unobserved gamma-decay to door-way states around 11 MeV in Si-28.

The radiative capture process of the 12 C +12 C and 12 C +16 O reactions has been studied using the very selective 0° Dragon spectrometer at Triumf and its associated BGO γ-array. The experiments have been performed at energies around the Coulomb barrier where resonances in the process have been reported. Our results show previously unobserved γ-decay to doorway states in the 24 Mg and 28 Si respectively around 10 to 12 MeV. The nature of the states is discussed and two scenarii are proposed.

The deuteron-emission channel in the beta decay of the halo nucleus (11)Li was measured at the Isotope Separator and Accelerator facility at TRIUMF by implanting postaccelerated (11)Li ions into a segmented silicon detector. The events of interest were identified by correlating the decays of (11)Li with those of the daughter nuclei. This method allowed the energy spectrum of the emitted deuterons to be extracted, free from contributions from other channels, and a precise value for the branching ratio B(d)=1.30(13)x10(-4) to be deduced for E(c.m.)>200 keV. The results provide the first unambiguous experimental evidence that the decay takes place essentially in the halo of (11)Li and that it proceeds mainly to the (9)Li+d continuum, opening up a new means to study the halo wave function of (11)Li.

The nuclide Ti-44 is predicted to be produced in significant quantities in core-collapse supernovae, and indeed it has been observed in the supernova remnant Cassiopeia-A by space-based gamma-ray telescopes. The main production of Ti-44 takes place in the alpha-rich freeze-out phase deep inside the supernova. The key reactions governing the Ti-44 abundance have been identified in an earlier sensitivity study. Using the recoil mass spectrometer DRAGON at the TRIUMF-ISAC facility in Vancouver, Canada, we measured the main production reaction Ca-40(alpha,gamma)Ti-44, resulting in an increased reaction rate compared to the rate derived from previous prompt gamma-ray studies, which is commonly used in supernova models. The uncertainty of the Ti-44 production is now dominated by the rate of reactions with short-lived nuclides around Ti-44, namely V-45(p,gamma)Cr-46, Ti-44(alpha, p)V-47 and Ti-44(alpha,gamma)Cr-48. The sensitivity of these reactions on the Ti-44 production has been revisited.

The deuteron-emission channel in the beta decay of the halo nucleus (11)Li was measured at the Isotope Separator and Accelerator facility at TRIUMF by implanting postaccelerated (11)Li ions into a segmented silicon detector. The events of interest were identified by correlating the decays of (11)Li with those of the daughter nuclei. This method allowed the energy spectrum of the emitted deuterons to be extracted, free from contributions from other channels, and a precise value for the branching ratio B(d)=1.30(13)x10(-4) to be deduced for E(c.m.)>200 keV. The results provide the first unambiguous experimental evidence that the decay takes place essentially in the halo of (11)Li and that it proceeds mainly to the (9)Li+d continuum, opening up a new means to study the halo wave function of (11)Li.

The heavy-ion radiative capture reaction 12C(16O,γ)28Si has been studied at three energies on- (ELab = 20.0 and 21.2 MeV) and off- (ELab = 20.7 MeV) resonance at Triumf (Vancouver) using the state-of-the-art Dragon 0° spectrometer and its very efficient associated BGO γ array. Intermediate states around Ex = 11.5 MeV, carrying a large part of the resonant flux have been observed for the first time in this system. The nature of those doorway states is discussed in terms of recently calculated cluster bands in 28Si. The results are compared to a recent similar investigation of the 12C(12C,γ)24Mg reaction.

The nuclide Ti-44 is predicted to be produced in significant quantities in core-collapse supernovae, and indeed it has been observed in the supernova remnant Cassiopeia-A by space-based gamma-ray telescopes. The main production of Ti-44 takes place in the alpha-rich freeze-out phase deep inside the supernova. The key reactions governing the Ti-44 abundance have been identified in an earlier sensitivity study. Using the recoil mass spectrometer DRAGON at the TRIUMF-ISAC facility in Vancouver, Canada, we measured the main production reaction Ca-40(alpha,gamma)Ti-44, resulting in an increased reaction rate compared to the rate derived from previous prompt gamma-ray studies, which is commonly used in supernova models. The uncertainty of the Ti-44 production is now dominated by the rate of reactions with short-lived nuclides around Ti-44, namely V-45(p,gamma)Cr-46, Ti-44(alpha, p)V-47 and Ti-44(alpha,gamma)Cr-48. The sensitivity of these reactions on the Ti-44 production has been revisited.

H. Fujikawab, S. Hayakawab, N. Iwasak, J. J. Heb, D. Kahla, L. H. Khiemb, S. Kubonob, Y. Kurihawab, Y. K. Kwond, J. LeNestoura, G. Lorussoc,l, M. Matosc,l, J Y. Moond, M. Niikurab, S. Nishimurag, A. Odahara f , C. V. Ouelleta, J. Pearsona, J. Pereirac,l, R. Pizzonei, A. Saitob, H. Schatzc,l, A. Signoraccic,l, C. Signorini j, A. Smitha, K. Smithc,l, T. Teranishie, Y. Toganoh, B. Walesa, Y. Wakabayashib, D. Weisshaarc,l, H. Yamaguchib, R. Zegersc,l aDepartment of Physics and Astronomy, McMaster University, Canada bCenter for Nuclear Study, Graduate School of Science, University of Tokyo, Japan cNational Superconducting Cyclotron Laboratory, Michigan State University, USA dDepartment of Physics, Chung-Ang University, South Korea eDepartment of Physics, Kyushu University, Japan f Department of Physics, Nishinippon Institute of Technology, Japan gRIKEN (The Institute of Physical and Chemical Research) hDepartment of Physics, Rikkyo University, Japan iDepartment of Physics, University of Catania and INFN, Italy jDepartment of Physics, University of Padova and INFN, Italy kDepartment of Physics, Tohoku University, Japan lDepartment of Physics, Michigan State University, USA

The radiative capture process of the C-12 + C-12 and C-12 + O-16 reactions has been studied using the very selective 0 degrees Dragon spectrometer at Triumf and its associated BGO gamma-array. The experiments have been performed at energies around the Coulomb barrier where resonances in the process have been reported. Our results show previously unobserved gamma-decay to doorway states in the Mg-24 and Si-28 respectively around 10 to 12 MeV. The nature of the states is discussed and two scenarii are proposed.

The DRAGON facility at TRIUMF/ISAC detects reaction products following radiative capture of a hydrogen or helium target nucleus by an accelerated heavy ion. Capture reactions of interest in nuclear astrophysics may have reaction rates 10–14 orders of magnitude lower than the intensity of the incident beam: as well as efficiently transporting the heavy reaction product from the target to a suitable particle detector, the separator must provide most of the suppression of unreacted beam. We describe the features of beam background encountered in a range of proton- and alpha-capture experiments at the DRAGON facility.

The heavy-ion radiative capture reaction 12C(16O,γ)28Si has been studied at three energies on- (ELab = 20.0 and 21.2 MeV) and off- (ELab = 20.7 MeV) resonance at Triumf (Vancouver) using the state-of-the-art Dragon 0° spectrometer and its very efficient associated BGO γ array. Intermediate states around Ex = 11.5 MeV, carrying a large part of the resonant flux have been observed for the first time in this system. The nature of those doorway states is discussed in terms of recently calculated cluster bands in 28Si. The results are compared to a recent similar investigation of the 12C(12C,γ)24Mg reaction.

The decay rate of Na-22 implanted in aluminium has been measured at room temperature and at 10 K. The rate should increase by 40% according to Rolfs (2006 Public Lecture for SLENA (Kolkata, India)) and by about 6% according to Limata et al (2006 Eur. Phys. J. A 28 251). In the latter publication, an increase of only 1.2 +/- 0.2% has been measured and the deviation has been assigned to an incomplete implantation of Na-22 in the palladium sheet. Contrary, the source used for our measurements has been made by a 70 MeV proton beam penetrating an aluminum sheet, therefore the Na-22 was produced deep inside the metal and the full effect should be visible when cooling the sample. We did not see an enhanced decay rate within the precision limit (0.04%) of our measurement.

The DRAGON (Detector of Recoils And Gammas Of Nuclear reactions) is used to measure radiative proton and alpha capture reaction rates involving both stable and radioactive, heavy-ion reactants at the TRIUMF-ISAC high intensity radioactive beam facility. Completed in 2001 it has been used for several challenging studies for nuclear astrophysics, e.g. 12C(α, γ)16O, 21Na(p, γ)22Mg, 26gAl(p, γ)27Si and 40Ca(α, γ)44Ti. Since initial operation, a number of improvements have been incorporated which are described here. These include a beam centering monitor based on a CCD camera, a mechanical iris to skim of beam halo, a solid state stripper acting as a charge state booster for beams with A≳30, beta and gamma detectors to monitor beam intensity and to determine beam contamination in experiments with radioactive beam and the ionization chamber for both recoil identification and isobar separation.

We measured the P-decay of the halo-nucleus Li-11, with particular attention to the deuteron- and triton-emission channels. We employed a post-accelerated beam of Li-11 ions, and the implantation technique in a finely-segmented silicon detector. The channels of interest were identified through the time and space correlations between the implantation events and the parent and daughter decays. We obtained the branching ratios, as well as the spectra of the emitted ions.